The invention relates generally to self-propelled machines and, more particularly, to a method and apparatus for determining the distance between an agricultural machine and the ground.
It is known that at least one mechanical ground probe can be mounted on a front attachment of an agricultural machine. This probe determines the distance of the front attachment from the surface of a field. A control device connected to its output controls the height of the front attachment above the field surface as a function of the distance sensed. Further, it is known, for example from DE 38 07 610 C2, that several ground probes can be arranged on the front attachment and distributed across the working width. The ground probes are spring-loaded and act mechanically on the standing crop or on the ground. The distance sensed by each probe is used by a control device for automatic height adjustment of the front attachment above the field or for automatic adjustment of the transverse tilt of the front attachment. The arrangement shown in DE 38 07 610 C2 allows only for limited penetration of field stubble or for the compaction of weeds. The penetration or compaction leads to improved distance measurement and, thus, fewer harvesting losses. Such results, however, are achieved only behind the finger bar of the cutterbar. The best performance of the mechanical ground probes is achieved only in a thin standing crop or in a weed-free area and between the individual rows.
A further drawback results from the mechanically limited measuring range of the ground probes. The ground probes cannot be used, for example, when harvesting seed because the probes have no contact with the ground when the front attachment is at the required working height. Further, such ground probes are subject to mechanical wear and damage. They must, therefore, be structurally elaborate for this purpose and be designed for turning and reversing.
It is further known, for example from DE 44 06 892 A1, that the distance between a front attachment and a field surface can be scanned contactlessly by ground distance sensors arranged on the front attachment. An ultrasound sensor scans, with reference to the propagation time of a transmitted and received wave pulse, the distance from the surface of the field to the height of the sensor. The use of an ultrasound sensor for this application has the drawback that, in case of dense ground cover or heavy weed invasion, the distance from the ground is not determined but instead the distance from the ground cover or weeds. The ultrasound wave transmitted is reflected directly on the nearest obstacle, and this is the distance sensed as the distance from the ground. This often results in establishing the front attachment at a setting too high above the ground. Incorrectly setting the height of the front attachment results in inefficiencies. For example, crop lying on the ground is no longer picked up by the front attachment or the crop is not completely harvested.
It is an aspect of the invention to provide a device which allows for contactless determination of the distance of the agricultural machine from the ground.
In another aspect of the invention, the distance between a front attachment and the ground is determined through the use of a sensor which penetrates vegetation.
In yet another aspect of the invention, the penetrating sensing means is used to automatically control the height or tilt of the front attachment.
The above aspects are achieved by the fact that associated with the agricultural machine is a sensor which contactlessly determines the distance from the ground by means of a electromagnetic wave, such as a radar or micro wave, penetrating through the field vegetation. The use of an electromagnetic wave of this kind allows reliable detection of the distance from the ground, as it penetrates through the field vegetation such as cereals, stubble, weeds or an undersown crop.
The focused electromagnetic wave is oriented substantially vertically towards the ground, past the field vegetation. The approximately vertical orientation allows for scanning along the field vegetation to the ground with at little disturbance as possible by the vertically growing field vegetation, for example blades of grass or stubble. Due to focusing of the electromagnetic wave, the scanning area of the scanning beam is punctiform and needs only a minimum window to the ground in order to be able to scan it reliably. In particular, this scanning beam penetrates to the ground as low as possible past the field vegetation.
The sensor is arranged on the front attachment of the agricultural machine. This arrangement allows early detection of the distance from the ground. Further, the sensor can be designed with a lower measuring distance/scanning distance, so that the costs of the sensor are lower. A further advantage with this arrangement arises due to direct variation of the measured distance upon adjustment of the front attachment in position relative to the ground. The altered setting is detected directly by the sensor so that further sensors for detecting the position of the front attachment are unnecessary. Arranging the sensor on the front attachment instead of using ground probes produces, with a low working height, the same functionality of ground height imitation for the front attachment. However, with greater working heights, the difference is readily apparent. The sensors do not lose contact with the ground, and ground height imitation is achieved even with greater working heights. Also, without great expenditure, this arrangement affords the possibility of orienting the scanning beam of a laser sensor vertically or perpendicularly towards the ground.
The sensor provides a parameter used for automatic adjustment and/or control of the agricultural machine. Automatic control of the agricultural machine is possible by this means, and in particular the agricultural machine is automatically adjusted to the corresponding parameters already before harvesting the sensed field vegetation. This takes place contactlessly and without an additional sensor. Advantageously, harvesting can be carried out with optimized adjustment of the agricultural machine, or tracking can be improved.
In an alternative embodiment, a laser sensor is suitable as the sensor. This laser sensor scans the distance from the ground with a point laser beam by measurement of the propagation time, and advantageously also determines, due to the approximately vertical arrangement and the highly focused form of the laser beam past the field vegetation, the distance from the ground. The laser sensor is conveniently mounted to a divider of the front attachment. Due to the movement of the agricultural machine and the function of the divider, the field vegetation is scanned advantageously and new xe2x80x9cwindowsxe2x80x9d to the ground are traversed constantly, so that the ground can be detected continuously.